The measurement of CO2 in tissues (cells) of a patient who is in a critical condition, such as a heart attack or bleeding patient being resuscitated, is a good indicator of the effectiveness of blood circulation in the patient. In our earlier U.S. Pat. Nos. 5,579,763 and 6,055,447 we described the measurement of CO2 by placing a sensor against mucosal tissue under the tongue, and sealing the volume under the tongue to prevent air flow that would carry away CO2 and therefore affect CO2 measurements. This required a person, such as a caregiver, to hold the apparatus in place. If a region immediately around the location where a CO2 sensor was in contact with a mucosal surface could be reliably sealed, without requiring a caregiver to continually hold the apparatus in place with his/her hand, this would provide more reliable measurements of CO2, temperature or other measurable conditions of the patient and free the caregiver to perform other tasks.